Computer controller systems such as those disclosed in U.S. Pat. No. 3,686,639 entitled "Digital Computer-Industrial Controller System and Apparatus", have been utilized in recent years to control many industrial operations such as automatic assembly equipment, textile machinery, materials handling equipment, and chemical processes. Computer controller systems have generally utilized core memories in order to store variable information relating to electrical circuit lines found in standard electrical circuit ladder diagrams commonly used in industrial control systems. These core memories require a significant amount of peripheral electronic circuitry in order to properly write-in and read-out information. Because of these inherent problems encountered with core memories and also because of their relatively high price, computer controller systems have not been readily adaptable to small industrial control systems utilizing from 10 to 30 simulated outputs and from 20 to 60 input signals.
During the last several years, new methods of storing variable data have been developed in the electronic industry. Thus the use of integrated circuit random access memories has allowed the electronic designer to store and retrieve variable information without the need for core memories. However, such electronic memory devices are unable to retain stored information upon de-energization of the integrated circuits. Therefore, such integrated circuits are unable to be utilized in storing electrical circuit line information if the system is periodically de-energized either for work shutdowns or during power failures.
Recently however, the Intel Corporation of Santa Clara, California has invented memory chips which are able to retain stored information regardless of the energized state of the memory chip. Information is electrically written into the chip but only ultraviolet light is able to erase the memory chip. Since the ultraviolet light erases the entire memory of the chip, selective erasure of information within the memory chip is unobtainable.
Some manufacturers of electronic equipment have utilized Intel Corporation's ultraviolet "read only" memory chips in various electronic devices including industrial computer controllers. However, these manufacturers require that the delicate memory chip be physically removed from the electronic structure when reprogramming of the memory chip is desired. Such a technique is highly undesirable in industrial computer controllers since these controllers are commonly used in very harsh industrial environment where soot, oil and grime are frequently found. In addition, the removal of the memory chip in an industrial controller system requires that the equipment being controlled be shutdown during the removal and reprogramming of the memory chip. Such shutting down of highly expensive equipment is of course undesirable; and also, since a desired change may require more than one adjustment to the industrial controller, repeated removals of the memory chip from the controller may be necessary.
The present invention eliminates these problems by reprogramming the memory chips without physically removing them from the central processor in which they are located. In addition, the present invention allows the operator to vary the electrical circuit line network or control program without shutting down the controller. Therefore, "on-line" de-bugging of the control program is possible with the present invention.
The present invention thus allows the operator to observe the present electrical circuit line network, to reprogram this network, and to store this reprogrammed network into the memory chips while the industrial computer controller system is operating. In addition, the present invention provides a "trace" feature which greatly facilitates de-bugging the control program by allowing the operator to view the entire electrical circuit line to which an electrical element in a presently viewed electrical circuit line has its state referenced. Furthermore, the present invention provides a "scroll" feature that allows the operator to sequentially view higher or lower numbered electrical circuit lines of the electrical circuit diagram. The present invention also allows the operator to disable any electrical circuit line without the need for erasing the entire memory chips and reprogramming the chips with the previous control program minus the disabled circuit line. In addition, the present invention allows a new electrical circuit line to be programmed into the memory chips without first erasing the entire memory chips.
Thus the present invention is a miniaturized computer controller system providing relay type logic as well as timers and counters for controlling industrial control systems having relatively few inputs and outputs. The present invention is compact, rugged, and inexpensive and so is readily suited for small industrial systems including designers and manufacturers of automatic machine tools.